The objective of laser-aided edge diagnostics is closely connected with plasma wall interaction processes. Thus at first a short description of the plasma regions near first wall, limiter or divertor and the most important quantities and processes to be evaluated there is given. A very important technique to measure electron densities and temperatures in the edge is Thomson scattering. Collective scattering represents a useful method to quantify fluctuations of electron density and their relation to particle and energy transport. To detect neutral particles and ions after their release from the wall and during recycling phases laser induced fluorescence (LIF) is a well established technique. Future applications of laser diagnostics as two-photon scattering and coherent anti-Stokes Raman scattering (CARS) are discussed.
IV. SUMMARY AND CONCLUSION
The most important methods of laser aided edge diagnostics are introduced and a few results of measurements summarized. While Thomson scattering on tokamaks seems to be now a matter of routine with high reliability, LIF techniques still underly restrictions because nearly each atomic species requires its own laser system, often in the VUV. Nevertheless, some progress can be observed with respect to the bandwidth, timing range, wavelength, power, reproducibility, repetition rate etc. It is anticipated that excitation by two-photon absorption develops more and more to a sensitive technique as this is expected from four-wave mixing techniques.